A typical blade system includes a chassis for holding several “blades”. Each blade can include one or more processor nodes, each of which includes one or more processors and associated memory. The chassis can include a backplane that provides power and connectivity, input/output (I/O) connectivity including network connectivity and inter-blade connectivity. In some blade systems, front connector bars spanning two or more blades provide or supplement inter-blade connectivity. In some blade systems, the inter-blade connectivity provides for cache coherent operation among processor blades associated with different blades. This allows a set of blades to operate as a single more powerful computer rather than as a network of separate computers that happen to be to the same chassis. Blade systems can be upgraded conveniently by swapping previous-generation blades with more capable newer-generation blades. In this sense, blade systems provide a hedge against obsolescence and allow a customer's investment to be amortized over a longer time, decreasing the overall cost of ownership.